Tuesday, November 10, 2009

Dinosaur Running and Endothermy in PLoS ONE

On a personal note, I have recently stepped up as "Section Editor" for paleontology at PLoS ONE. This means that I'll be coordinating the editorial flow for most paleo-themed papers that come the journal's way.

One of the real joys of editing for a major journal like PLoS ONE is getting a "sneak peak" at some pretty nifty research. Today, Herman Pontzer, Vivian Allen, and John Hutchinson have a new paper that should be of interest to this blog's general audience [full disclosure: I was the academic editor for this contribution]. As always, papers at PLoS ONE are free to download, comment upon, and rate.

The abstract and citation are copied below; for more info, check out the press release or Ed Yong's excellent blog post on the topic.

The bipedal and presumably endothermic Velociraptor. From the original by Matt Martyniuk, licensed under a Creative Commons Attribution ShareAlike 3.0 license.

Pontzer H, Allen V, Hutchinson JR (2009) Biomechanics of running indicates endothermy in bipedal dinosaurs. PLoS ONE 4(11): e7783. doi:10.1371/journal.pone.0007783

One of the great unresolved controversies in paleobiology is whether extinct dinosaurs were endothermic, ectothermic, or some combination thereof, and when endothermy first evolved in the lineage leading to birds. Although it is well established that high, sustained growth rates and, presumably, high activity levels are ancestral for dinosaurs and pterosaurs (clade Ornithodira), other independent lines of evidence for high metabolic rates, locomotor costs, or endothermy are needed. For example, some studies have suggested that, because large dinosaurs may have been homeothermic due to their size alone and could have had heat loss problems, ectothermy would be a more plausible metabolic strategy for such animals.

Methodology/Principal Findings
Here we describe two new biomechanical approaches for reconstructing the metabolic rate of 14 extinct bipedal dinosauriforms during walking and running. These methods, well validated for extant animals, indicate that during walking and slow running the metabolic rate of at least the larger extinct dinosaurs exceeded the maximum aerobic capabilities of modern ectotherms, falling instead within the range of modern birds and mammals. Estimated metabolic rates for smaller dinosaurs are more ambiguous, but generally approach or exceed the ectotherm boundary.

Our results support the hypothesis that endothermy was widespread in at least larger non-avian dinosaurs. It was plausibly ancestral for all dinosauriforms (perhaps Ornithodira), but this is perhaps more strongly indicated by high growth rates than by locomotor costs. The polarity of the evolution of endothermy indicates that rapid growth, insulation, erect postures, and perhaps aerobic power predated advanced “avian” lung structure and high locomotor costs.

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